Heavy rains have bombarded the area in the past 24 hours, saturating the ground and testing the limits of flood mitigation measures.
The evacuations included homes, schools and businesses in Santa Clara and Ivins.
Officials said retention pond was fed by the Tuacahn Wash, and filled up after heavy rains Tuesday morning.
Santa Clara authorities ordered residents and businesses below the pond to evacuate at about noon.
The dike broke about 45 minutes later, just before 1:00 p.m.
Officials said the dike is located along Tuacahn Wash near baseball fields and west of Snow Canyon Middle School in St. George.
Officials said the floodwaters from broken dike were flowing through residential streets.
The flooding and evacuations affected about 25 homes and several businesses in a strip mall.
Between 25 and 30 homes and a dozen businesses were damaged by the flooding.
The Washington County School District reported that Santa Clara Elementary, Snow Canyon High, Snow Canyon Middle would be dismissed at their regular time, while students that live in the Santa Clara valley would be held at school until authorities deemed it safe to transport them home or to shelters.
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Meanwhile, students that live on the Santa Clara Heights, Ivins, Dixie Downs areas will be dismissed and transported home at their regular time.
The district later reported that flooding had disrupted the transportation of students, and suggested that some parents might need to pick up their children.
Parents were asked to check the Washington School District website for up to date information at http://washk12.org/.
A Red Cross reception center was opened for evacuees at the Santa Clara City Building (1st floor) at 2603 Santa Clara Drive. Red Cross officials said they were prepared to transition the center into a shelter, should the need arise.
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